Collagen-like protein CLAC, precursor thereof and genes encoding the same

ABSTRACT

A novel human collagen-like protein CLAC occurring in brain amyloid and its precursor CLAC-P; genes encoding the same; cDNA of mouse CLAC-P and its deduced amino acid sequence; antibodies specific to these proteins; and methods of diagnosing treating and preventing Alzheimer&#39;s disease by using the same.

The present invention relates to a human-type collagen-like protein(CLAC) and a precursor thereof (CLAC-P) in amyloid that accumulates inAlzheimer's brain and forms senile plaques; and genes encoding them.Further the present invention relates to a cDNA and an amino acidsequences of mouse-type CLAC-P. The present invention also relates todevelopment of: a method for treating of Alzheimer's disease byinhibiting a mechanism of accumulation of amyloid proteins, a method fortreating Alzheimer's disease by inhibiting cell injury, and a method fordiagnosing Alzheimer's disease.

BACKGROUND OF THE INVENTION

Alzheimer's disease is a dementing neurodegenerative diseasecharacterized by formation of senile plaques and neurofibrillarydegeneration as well as degeneration of neurons. Senile plaques that aremost characteristic of this disease are lesions composed mainly ofamyloid-beta peptide (Aβ) derived from beta-amyloid presursor protein(βAPP) (Biochem Biopys Res Commun 122, 1131 (1984)), with apolipoproteinE (Brain Res 541, 163 (1984)) and a complement component C1q (ActaNeuropathol 57, 239 (1982)), etc being deposited. Aβ aggregates byitself, and formation of amyloid fiber is promoted by actions of non-Aβamyloid components such as apolipoprotein E (Nature 372, 92 (1994)) andC1q (J Neurosci Res 46, 58 (1996)) as above described. Aβ consisting of40-42 amino acids is secreted from various cells including neurons, andit is not toxic to cells at a normal concentration. However at a higherconcentration, Aβ aggregates and becomes toxic to neurons (Science 250,279 (1990)). In this process, it is known that several molecules such asRAGE (Nature 382, 685 (1996)) and scavenger receptor Aβ (Nature 382, 716(1996)) are present on the cell surface and act as receptors foraggregated Aβ. It seems that aggregation, accumulation, and toxicity tocells of amyloid are very important in neuronal degeneration process ofAlzheimer's disease; therefore, inhibition of these processes will be aneffective therapeutic method for Alzheimer's disease.

Accumulation of Aβ as amyloid is very characteristic of Alzheimer'sdisease, however it is being clarified that only accumulation of Aβ isnot sufficient for toxicity to neurons as well as for the development ofAlzheimer's disease (J. neurosci. 17, 7053 (1997)). On the other hand,as inferred from the fact that genetic polymorphism of proteins such asapolipoprotein E which promotes accumulation process of senile plaqueamyloid serves as a risk factor for development of Alzheimer's disease(Science 261, 921 (1993)). It has been noted that unknown proteinaceouscomponents in amyloid can greatly influence the accumulation andneuronal injury by amyloid; however the responsible components have notbeen identified yet.

SUMMARY OF THE INVENTION

Taking circumstances above mentioned into consideration, the inventorsproduced mouse monoclonal antibodies to an amyloid fraction extractedfrom of a brain of a patient with Alzheimer's disease, and surprisinglyfound a monoclonal antibody among these antibodies which selectivelystains senile plaque amyloid and biochemically recognizes a novelprotein of 50 to 100 kilodaltons.

Further the inventors studied the amyloid deposits on the basis of thesefindings, and found a novel human collagen-like Alzheimer amyloid plaquecomponent (CLAC), and succeeded in obtaining entire structure of CLACand cloning a novel gene encoding entire CLAC and a precursor thereof(CLAC-P). Further the inventors determined cDNA sequence of mouse-typeCLAC-P, and deduced the amino acid sequence.

The present invention relates to:

(1) CLAC DNA comprising a nucleotide sequence of nucleotide 868 tonucleotide 2493 shown in SEQ ID NO: 1,

(2) CLAC comprising an amino acid sequence of amino acid 113 to aminoacid 654 shown in SEQ ID NO: 2,

(3) A DNA encoding a protein in which one or plural amino acids areinserted into, deleted from, or substituted in CLAC defined in (2), saidencoded protein having following properties:

(a) accumulating in senile plaque amyloid component of Alzheimer'sdisease, and

(b) having a function of promoting aggregation of Aβ,

(4) A DNA which hybridizes to the DNA defined in (1) under a stringentcondition, and encodes a protein having the following properties:

(a) accumulating in senile plaque amyloid component of Alzheimer'sdisease, and

(b) having a function of promoting aggregation of Aβ,

(5) A protein encoded by a DNA defined in (3) or (4),

(6) CLAC-P DNA comprising a nucleotide sequence of nucleotide 532 tonucleotide 2493 shown in SEQ ID NO: 1,

(7) CLAC-P comprising an amino acid sequence shown in SEQ ID NO: 2,

(8) A DNA encoding a protein in which one or plural amino acids areinserted into, deleted from, or substituted in CLAC-P defined in (7),said encoded protein functioning as an Aβ receptor on cell surface,

(9) A DNA which hybridizes to a DNA defined in (6) under a stringentcondition and encodes a protein functioning as an Aβ receptor on cellsurface,

(10) A protein encoded by a DNA defined in (8) or (9),

(11) A protein defined in (10) in which one or more amino acids aredeleted from or substituted in a region of amino acid 141 to 146, oramino acid 589 to 597 shown in SEQ ID NO: 2,

(12) An expression vector containing a DNA defined in any one of (1),(3) and (4),

(13) A transformant transformed by a vector defined in (12),

(14) A method for producing a recombinant protein, which comprisesculturing a transformant defined in (13) under a condition enabling anexpression vector defined in (12) to be expressed,

(15) An expression vector containing a DNA defined in any one of (6),(8) and (9),

(16) A transformant transformed by a vector defined in (15),

(17) A method for producing a recombinant protein, which comprisesculturing a transformant defined in (16) under a condition enabling anexpression vector defined in (15) to be expressed,

(18) A transformant deposited to International Patent OrganismDepositary, National Institute of Advanced Industrial Science andTechnology (AIST Tsukuba Central 6, 1-1, Higashi 1-Chome, Tsukuba-shi,Ibaraki-ken, 305-8566, Japan) under accession No. FERM BP-7438,

(19) CLAC-P gene contained in a transformant defined in (18),

(20) A method for producing a recombinant protein, which comprisesculturing a transformant defined in (18) under a condition enabling avector contained therein that contains CLAC-P gene to be expressed,

(21) An antibody which specifically binds to a protein defined in (2) or(5),

(22) An antibody defined in (21) which is a monoclonal antibody 9D2,

(23) A method for screening an inhibitor of CLAC activity, whichcomprises using a protein defined in (2) or (5).

(24) An inhibitor of CLAC activity obtainable by a screening methoddefined in (23),

(25) A method for detecting CLAC, which comprises using an antibodydefined in (21),

(26) A method for treating of, delaying progress of, or preventingAlzheimer's disease, which comprises using an antibody defined in (21)or an inhibitor of CLAC activity defined in (24),

(27) A method defined in (25), in which the antibody is monoclonalantibody 9D2,

(28) A method defined in (26), in which the antibody is monoclonalantibody 9D2,

(29) A method for purifying CLAC, which comprises using monoclonalantibody 9D2,

(30) An antibody which specifically binds to a protein defined in anyone of (7), (10) and (11),

(31) An antibody defined in (30), which is monoclonal antibody 9D2,

(32) A method for screening an inhibitor of CLAC-P activity, whichcomprises using a protein defined in one of (7), (10) and (11),

(33) An inhibitor of CLAC-P activity obtainable by a screening methoddefined in (32),

(34) A method for detection of CLAC-P, which comprises using an antibodydefined in (30),

(35) A method for treating of, delaying progress of, or preventingAlzheimer's disease, which comprises using an antibody defined in (30)or an inhibitor of CLAC-P activity defined in (33),

(36) A method defined in (34), in which the antibody is monoclonalantibody 9D2,

(37) A method defined in (35), in which the antibody is monoclonalantibody 9D2,

(38) A method for purifying CLAC-P, which comprises using monoclonalantibody 9D2,

(39) A kit for diagnosing Alzheimer's disease, which comprisesdetectably labeled monoclonal antibody 9D2,

(40) A transgenic animal in which a DNA defined in any one of (1), (3),(4), (6), (8) and (9) is artificially inserted into, or deleted from thechromosome.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show CLAC-P cDNA nucleotide sequence (SEQ ID NO: 1) anddeduced amino acid sequence corresponding thereto (SEQ ID NO: 2),respectively

FIG. 2 shows 9D2 immunostaining of HEK293 cells expressing CLAC-P (leftpanel, A) and Western blot of a HEK293 cell membrane fraction expressingCLAC-P (right panel, B).

FIG. 3 shows cDNA nucleotide sequence of mouse CLAC-P (SEQ ID NO: 48).

FIG. 4 shows deduced amino acid sequence of mouse CLAC-P (SEQ ID NO:49).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first aspect of the present invention is a DNA comprising anucleotide sequence of nucleotide 868 to nucleotide 2493 shown in SEQ IDNO: 1, which encodes CLAC.

The second aspect of the present invention is CLAC having an amino acidsequence of amino acid 113 to amino acid 654 shown in SEQ ID NO: 2.

Novel amyloid molecules CLAC and CLAC-P of the present invention can bedetected by use of specific interaction with antibodies, as described inExample 2. Partial amino acid sequences, cDNA sequence, and amino acidsequence thereof can also be determined. These procedures are brieflydescribed below.

CLAC and CLAC-P can be detected, for example by following methods:

A mouse, for example BALB-C mouse is immunized with senile plaqueamyloid components which are partially purified as an insoluble fractionfrom brain of a patient with Alzheimer's disease by known methods suchas sucrose density gradient centrifugation and urea extraction, and thenantibodies, preferably a monoclonal antibody is obtained. Using theantibody thus obtained, CLAC and CLAC-P can be detected according to amethod (i) or (ii) described below:

(i) After cerebral cortex obtained from a patient with Alzheimer'sdisease is fixed in 10% formalin, tissue sections are immunochemicallystained, and CLAC or CLAC-P is detected as an amyloid plaque, or

(ii) After cerebral cortex obtained from a patient with Alzheimer'sdisease is extracted with Tris-buffer and sodium dodecyl sulfate, theprecipitation thus formed is dissolved in 70% formic acid to obtain anamyloid fraction. The amyloid fraction is subjected toSDS-electrophoresis and Western blot analysis, and CLAC or CLAC-P isdetected as a polypeptide of 50 to 100 kilodaltons.

Preferable antibody used is monoclonal antibody 9D2 described in Example1.

Partial amino acid sequences of CLAC of the present invention can bedetermined, for example by following steps (i) to (v):

(i) After cerebral cortex obtained from a patient with Alzheimer'sdisease is extracted with Tris-buffer and sodium dodecyl sulfate (SDS),the precipitation thus formed is dissolved in 70% formic acid. Amyloidcomponent thus obtained is submitted to reverse phase high performanceliquid chromatography (HPLC), and fractionated to be separated from Aβpeptide,

(ii) 50 kDa and 100 kDa polypeptides are isolated respectively by gelfiltration column,

(iii) The polypeptide is partially hydrolyzed by a protease such aslysylendopeptidase, Asp-N or trypsin,

(iv) Peptide fractions are separated by reverse phase HPLC, and

(v) The amino acid sequence of the peptide is determined by an aminoacid sequence analyzer.

cDNA nucleotide sequence of a precursor of CLAC, i.e. CLAC-P can beobtained by, for example a method comprising following steps (i) and(ii):

(i) Using synthetic oligonucleotide mixture (degenerate primers) asprimers which correspond to nucleotide sequence encoding a part of apartial amino acid sequence of CLAC obtained as mentioned above, forexample a part of Gly Glu Gln Gly Asp Gln Gly Pro Arg Met Val Phe ProLys Ile Asn His Gly Phe Leu Ser Ala Asp Gln Gln Leu Ile Lys (SEQ ID NO:11), cDNA encoding a part of CLAC protein is cloned from a complementaryDNA (cDNA) library of human brain by use of polymerase chain reaction(PCR), and

(ii) Using the nucleotide sequence obtained in step (i) as a template,“rapid amplification of cDNA ends” method known in the art is repeated.

Also, deduced entire amino acid sequence can be obtained by translatingthe nucleotide sequence above mentioned into an amino acid sequenceaccording to a standard method.

The cDNA sequence of human CLAC-P thus obtained is shown in SEQ IDNO: 1. This sequence has an ORF (open reading frame) (nucleotides 532 to2493) encoding CLAC-P consisting of 654 amino acids, and the deducedentire amino acid sequence of CLAC-P of the 654 amino acids is shown inSEQ ID NO: 2.

Alternatively, using cDNA library derived from mouse or rat brain, andby synthesizing oligonucleotides corresponding to the nucleotidesequence appropriately selected from human CLAC-P nucleotide sequence,and using them as primers, PCR method can be performed to obtain mouseor rat CLAC-P cDNA and amino acid sequences thereof.

CLAC of the present invention has following functions: (a) itaccumulates in senile plaque amyloid of Alzheimer's disease, (b) itpromotes aggregation of Aβ.

Function of CLAC of the present invention to promote Aβ aggregation canbe estimated by various methods, for example following methods (1) or(ii):

(i) One hundred and fifteen μM of synthetic Aβ (1-42) peptide [whichmeans that the peptide consists of amino acids 1 to 42 from theN-terminal] and an appropriate amount of purified CLAC are mixed, andincubated for 0 to 5 days at room temperature. The reaction mixture iscentrifuged at 15,000×g for 15 min, and the precipitation is suspendedin 10 μl of PBS solution. An appropriate amount of thioflavin T isadded, and analysis is performed in a fluorescence photometer. λex is440 nm, and λem is 482 nm. Fluorescence obtained is compared with thatobtained by incubation with Aβ (1-42) only (without purified CLAC),

alternatively (ii) it is immunochemically or biochemically identifiedthat more beta-amyloid plaques are found in brain of a mouse generatedby mating a transgenic mouse over-expressing human CLAC-P gene with amouse over-expressing Alzheimer mutant βAPP gene, than in brain of atransgenic mouse expressing excess Alzheimer mutant βAPP gene only; orit is immunochemically or biochemically identified that lessbeta-amyloid plaques are found in a CLAC-P gene knock-out mouseover-expressing Alzheimer mutant βAPP gene, than in a transgenic mouseover-expressing Alzheimer mutant βAPP gene.

The third aspect of the present invention is a DNA encoding variant CLACprotein, in which one or plural amino acids are inserted into, deletedfrom, or substituted in CLAC amino acid sequence, said variant CLACprotein (a) accumulates in senile amyloid component of Alzheimer'sdisease, and (b) promotes Aβ aggregation.

Here, insertion, deletion or substitution of one or plural amino acidscan be occurred artificially or naturally. For example, by known methodsin gene-engineering such as site-specific mutagenesis (M. J. Zoller etal., Methods in Enzymology, 100, 468 (1983)) or PCR method (MolecularCloning 2nd Ed. Ch. 15, Cold Spring Harbor Laboratory Press (1989)),these mutations can be occurred. In addition such insertion, deletion orsubstitution of one or plural amino acids can be occurred in vivo.Variants such as splice variants and allelic variants are included invariant CLAC protein of the present invention. Moreover partial peptidesof CLAC which have the functions (a) and (b) above mentioned areincluded in variant CLAC protein of the present invention. Proteins inwhich one or plural amino acids are chemically modified (artificial ornaturally occurring) are also included in variant CLAC protein of thepresent invention. Such modifications include, for example acetylation,amidation, acylation, addition of sugar chain, phosphorylation,sulfation, addition of lipid, halogenation, formation of salt, etc.Moreover amino acids other than naturally occurring twenty L-amino acids(such as D-amino acids, artificial amino acids) can exist in variantCLAC protein. Homology of a DNA sequence encoding such a variant CLACprotein to a DNA sequence encoding the original CLAC (the first aspectof the present invention) is at least 50%, preferably at least 70%, morepreferably at least 80%, most preferably at least 90%.

Here, homology means a degree of match between two nucleotide sequencesor amino acid sequences, which is expressed by percentage. Currentlycomputer software-programs such as Smith-Waterman algorithm, FASTA orBLAST program, etc. are used to determine homology.

The fourth aspect of the present invention is a DNA which hybridizes tothe DNA defined in SEQ ID NO: 3 under a stringent condition, and encodesa protein having the following properties: (a) accumulating in senileplaque amyloid component of Alzheimer's disease, and (b) having afunction of promoting aggregation of Aβ. Here, “stringent condition”means a condition, for example in which hybridization occurs only whenthe nucleotide sequences have more than 90% homology. As example ofstringent condition is: incubation at 42° C. overnight in a solutioncontaining 50% formamide, 5×SSC (150 mM NaCl, 15 mM sodium citrate), 50mM sodium phosphate (pH 7.6), 5× Denhart's solution, 10% dextransulfate, and 20 ug/ml of danatured and sheered salmon sperm DNA, thenwashing in 0.1×SSC at 65° C. Hybridization and washing can be performedby known methods described in for example, Molecular Cloning 2nd Ed. Ch.11, Cold Spring Harbor Laboratory Press (1989) etc.

The fifth aspect of the present invention is a protein encoded by eitherDNA:

(i) a DNA encoding a variant CLAC protein in which one or plural aminoacids are inserted into, deleted from, or substituted in CLAC proteinshown in SEQ ID NO: 4, said variant CLAC protein (a) accumulates insenile plaque component of Alzheimer's disease, and (b) promotes Aβaggregation; or

(ii) a DNA hybridizing to the DNA shown in SEQ ID NO: 3 under astringent condition, said DNA encodes a protein which (a) accumulates insenile plaque component of Alzheimer's disease, and (b) promotes Aβaggregation.

Such proteins include variant CLAC proteins and proteins having highamino acid sequence homologies to CLAC, which have the functions (a) and(b) above mentioned. Embodiments of such proteins include for examplevariant CLAC proteins above described, partial peptides of CLAC, and rator mouse CLAC, etc.

In this specification, CLAC of the second aspect and variant CLAC of thefifth aspect can be collectively referred to “CLAC”.

The sixth aspect of the present invention is CLAC-P DNA comprises anucleotide sequence of nucleotide 532 to nucleotide 2493 shown in SEQ IDNO: 1.

The seventh aspect of the present invention is CLAC-P comprises an aminoacid sequence shown in SEQ ID NO: 2.

CLAC-P of the present invention functions as an Aβ receptor on cellsurface.

Function of CLAC-P of the present invention as an beta-amyloid receptorcan be estimated by various methods, for example following method:

HEK293 cells permanently expressing CLAC-P and control cells arecultivated to confluent state, and 10 μM Aβ (1-42) preincubated in atube for 60 min is added, and incubated for 60 min. Cells collected aresolublized with SDS sample buffer by sonication, and separated bySDS-polyacrylamide gel electrophoresis, and Western blotting isperformed using anti-Aβ antibody, then an amount of Aβ bound to cellscan be determined.

Cytotoxicity of Aβ bound to cells via CLAC-P can be estimated byfollowing method: for example, PC 12 cells having been induced todifferentiate to nerve cells are made to transiently express CLAC-P bylipofection method, and Aβ (1-42) preincubated for 1 hr is added, andincubated for 1 hr. Thereafter cells are fixed by 10% formalin, andnuclei showing apoptosis are stained by TUNEL staining, and then ratioof positive cells is compared with that of PC12 cells which do notexpress CLAC-P. Alternatively,3-[4,5-dimethylthiazole-2-yl]-2,5-diphenoltetrazolium bromide (MTT)reagent is added to each well, and amount of MTT reagent incorporatedinto living cells may be measured by a spectrophotometer and compared.

The eighth aspect of the present invention is a DNA encoding variantCLAC-P protein in which one or plural amino acids of CLAC-P areinserted, deleted or substituted, said variant CLAC-P protein functionsas an Aβ receptor on cell surface.

Here, insertion, deletion or substitution of one or plural amino acidscan be occurred artificially or naturally. For example, by known methodsin gene-engineering such as site-specific mutagenesis (M. J. Zoller etal., Methods in Enzymology, 100, 468 (1983)) or PCR method (MolecularCloning 2nd Ed. Ch. 15, Cold Spring Harbor Laboratory Press (1989)),these mutations can be occurred. In addition such insertion, deletion orsubstitution of one or plural amino acids can be occurred in vivo.Variants such as splice variants and allelic variants are included invariant CLAC-P protein of the present invention. Moreover partialpeptides of CLAC-P which functions as an Aβ receptor on cell surface areincluded in variant CLAC-P protein of the present invention. Proteins inwhich one or plural amino acids are chemically modified (artificial ornaturally occurring) are also included in variant CLAC-P protein of thepresent invention. Such modifications include, for example acetylation,amidation, acylation, addition of sugar chain, phosphorylation,sulfation, addition of lipid, halogenation, formation of salt, etc.Moreover amino acids other than naturally occurring twenty L-amino acids(such as D-amino acids, artificial amino acids) can exist in variantCLAC-P protein. Homology of a DNA sequence encoding such a variantCLAC-P protein to a DNA sequence encoding the original CLAC-P (the sixthaspect of the present invention) is at least 50%, preferably at least70%, more preferably at least 80%, most preferably at least 90%.

The ninth aspect of the present invention is a DNA hybridizing to a DNAshown in SEQ ID NO: 1 in a stringent condition, which encodes a proteinthat functions an Aβ receptor on cell surface.

The tenth aspect of the present invention is a protein encoded by eitherDNA:

(i) a DNA encoding a variant CLAC-P protein in which one or plural aminoacids of CLAC-P are inserted, deleted or substituted, said variantCLAC-P protein functions as an Aβ receptor on cell surface; or

(ii) a DNA hybridizing to the DNA shown in SEQ ID NO: 1 under astringent condition, said DNA encodes a protein which functions as an Aβreceptor on cell surface.

Such proteins include variant CLAC-P proteins and proteins having highamino acid sequence homologies to CLAC-P, which functions as an Aβreceptor on cell surface. Embodiments of such proteins include forexample variant CLAC-P proteins above described, partial peptides ofCLAC-P, and rat or mouse CLAC-P, etc.

Further, the eleventh aspect of the present invention is a splicevariant of CLAC-P of the present invention. Examples of splice variantsof CLAC-P of the present invention are a polypeptide shown in SEQ ID NO:2, in which one to six amino acids locating amino acid positions 141-146are deleted or substituted; or a polypeptide shown in SEQ ID NO: 2, inwhich one to nine amino acids locating amino acid positions 589-597 aredeleted or substituted; or a polypeptide shown in SEQ ID NO: 2, in whichboth deletion or substitution above described exist at the same time.Such a variety seems to be attributed to formation of plural kinds ofmessenger RNA by alternative selective splicing.

In this specification, CLAC-P of the seventh aspect, variant CLAC-Pprotein of tenth aspect, and splice variant of CLAC-P of eleventh aspectcan be collectively referred to “CLAC-P”.

The twelfth aspect of the present invention is an expression vectorcontaining a DNA any one of the first, the third, or the fourth aspectof the present invention. The thirteenth aspect of the present inventionis a transformant which is transformed by said expression vector. Thefourteenth aspect of the present invention is a method for producing arecombinant protein, which comprises culturing said transformant under acondition enabling said vector to be expressed. The recombinant proteinthus produced is also included in the present invention. Such arecombinant protein is CLAC of any one of the present invention, orvariant CLAC protein which (a) accumulates in senile plaque amyloidcomponent of Alzheimer's disease, and (b) promotes Aβ aggregation.

The fifteenth aspect of the present invention is an expression vectorcontaining a DNA of any one of the sixth, the eighth, or the ninthaspect of the present invention. The sixteenth aspect of the presentinvention is a transformant transformed by said expression vector. Theseventeenth aspect of the present invention is a method for producing arecombinant protein, which comprises culturing said transformant under acondition enabling said vector to be expressed. The recombinant proteinthus produced is also included in the present invention. Such arecombinant protein is CLAC-P of the present invention, or variantCLAC-P protein which functions as an Aβ receptor on cell surface. Inaspects relating these aspects, the present invention relates to aHEK293 cell transformant (deposited to International Patent OrganismDepositary, National Institute of Advanced Industrial Science andTechnology (AIST Tsukuba Central 6, 1-1, Higashi 1-Chome, Tsukuba-shi,Ibaraki-ken, 305-8566, Japan) under accession No. FERM BP-7438) in whicha vector is inserted that contains a gene encoding CLAC-P. Thus, thepresent invention also relates to the CLAC-P gene contained in thedeposited strain above mentioned. In further aspect, the presentinvention relates to a method for producing a recombinant protein, whichcomprises culturing the transformed strain deposited under a conditionenabling the vector therein containing CLAC-P gene to be expressed. Therecombinant protein thus produced is also included in the presentinvention.

Recombinant proteins can be produced by known methods in the art, forexample the method described in Molecular Cloning 2nd Ed., Cold SpringHarbor Laboratory Press (1989). Representative methods are described:

Vectors suitable for integration of DNA above described include, but arenot limited to pBR322 (Gene, 2, 95 (1977)), pBR325 (Gene, 4, 121(1978)), pUC12 (Gene, 19, 259 (1982)), pUC13 (Gene, 19, 259 (1982)),pUC118, pUC119 (Methods in Enzymology, 153, 3 (1987)) from Escherichiacoli, pUB110 (Biochemical and Biophysical Research Communication, 112,678 (1983)) from Bacillus. Other vectors can be used which can replicateand are maintained in the host.

A method for integration of the DNA above mentioned includes, forexample the method described in Molecular Cloning p. 239, Cold SpringHarbor Laboratory Press (1982).

A plasmid thus obtained is introduced into a suitable host such asEscherichia and Bacillus strains.

Examples of Escherichia strains are, but not limited to Escherichia coliK12DH1 (Proc. Natl. Acad. Sci. USA, 60, 160 (1986)), M103 (Nucleic AcidsResearch, 9, 309 (1981)), JA221 (Journal of Molecular Biology, 120, 517(1978)), HB101 (Journal of Molecular Biology, 41, 459 (1969)), C600(Genetics, 39, 440 (1954)).

A method for transformation includes, for example calcium chloridemethod described, or calcium chloride/rubidium chloride method describedin Molecular Cloning p. 249, Cold Spring Harbor Laboratory Press (1982).

Desired clones are selected from tranformants thus obtained, by knownmethods in the art such as colony hybridization method (Gene, 10, 63(1980)) and DNA sequencing method (Proc. Natl. Acad. Sci. USA, 78, 560(1977); Nucleic Acids Research, 9, 309 (1981)).

As described above, microorganism are obtained which retain a vectorcarrying a DNA containing cloned gene of the protein of the presentinvention.

Then, the plasmid is isolated from the microorganism.

A method for isolation includes, but not limited to alkali method (H. C.Birmbiom et al., Nucleic Acids Research, 1, 1513 (1979)).

A plasmid having DNA containing cloned gene of the protein of thepresent invention, can be used without treatment, or used after cleavageby restriction enzyme(s).

An expression vector can be obtained by ligating the cloned gene of theprotein of the present invention into downstream of a promoter of avehicle (vector) suitable for expression. Preferred hosts beingtransformed by the expression vector are animal cells, and preferredvectors include expression plasmids for animal cells (for example pcDNAI, pdKCR-dhfr, etc). Vectors suitable, for example, for bacterial cells,fungal cells, insect cells, plant cells can be used so long as they aresuitable for production of the recombinant proteins of the presentinvention, and such vectors are well known in the art.

Said gene may have ATG as a start codon (and optionally a nucleotidesequence encoding a suitable signal peptide) at the 5′ terminal, or mayhave TAA, TGA or ATAG (preferably TGA) as a termination codon at the 3′terminal. Further, promoter(s) is(are) connected to the upstream of thegene for expression.

Any expression promoters compatible with the host can be used in thepresent invention.

When the host is an animal cell, promoters derived from SV40, promotersof retroviruses (not limited to these) can be used, preferably SV40promoter is used.

Animal cells include, but not limited to monkey COS-7 cell, Chinesehamster ovary cells (CHO cells), neuroblastoma cells, glia cells,fibroblasts. Preferred cells are those that express and secrete muchprotein of the present invention, and particularly preferable cell ishuman embryonic kidney fibroblast 293 cell.

To transform animal cells, for example, the method described inVirology, 52, 456 (1973) is performed.

Thus, a transformant is obtained which has been transformed by a vectorcontaining DNA encoding the protein of the present invention.

When a transformant, the host of which is Escherichia or Bacillusstrain, is used, a liquid medium is suitable, in which carbon sources,nitrogen sources, minerals and so on necessary for growth of thetransformant are included. Examples of carbon sources are, but notlimited to, glucose, dextrin, soluble starch, and sucrose; examples ofnitrogen sources are, but not limited to, inorganic or organic materialssuch as ammonium salts, nitrates, corn steep liquor, corn starch,peptone, casein, meat extract, soybean meal, and potato extract;examples of minerals are, but not limited to, calcium chloride, disodiumhydrogenphosphate, and magnesium chloride. Yeast extract, vitamins,growth-promoting factors, etc may also be added to the medium.Preferably pH of the medium is about 6 to about 8.

Preferable medium for cultivation of Escherichia strains is, for exampleM9 medium containing glucose and casamino acid (Journal of Experimentsin Molecular Genetics, 431-433, Cold Spring Harbor Laboratory, New York(1972)). If necessary, an reagent such as 3beta-indoacrylic acid can beadded to the medium to make promoter effective.

When a host is Escherichia strain, usually cultivation is carried out atabout 15 to about 43° C., for about 3 to about 24 hours. If necessary,aeration and/or stirring can be added.

When a host is Bacillus strain, usually cultivation is carried out atabout 30 to about 40° C., for about 6 to about 24 hours. If necessary,aeration and/or stirring can be added.

When a transformant is cultured, the host of which is an animal cell,examples of media are, but not limited to, MEM medium (Science, 122, 501(1952)), DMEM medium (Virology, 8, 396 (1959)), RPMI 1640 medium (TheJournal of American Medical Association, 199, 519 (1967)), and 199medium (Proceeding of the Society for the Biological Medicine, 73 1(1950)). Five to 20% calf fetal serum can be added to these madia.Preferable pH of the media is about 6 to about 8. Usually cultivation isperformed at about 30 to about 40° C., and aeration and/or stirring isadded, if necessary.

Induced expression vector above described in which the gene of CALC-P orCLAC of the present invention is integrated, can be used not only for alarge scale production of the vector (by introducing the vector into abacterium such as Escherichia coli), or production of the recombinantprotein of the present invention in various cells, but also forproduction of transgenic animals as described below.

As above described, CLAC-P is a precursor of CLAC (CLAC is the fragmenttype thereof), and has an amino acid sequence shown in SEQ ID NO: 2.

Processing of CLAC-P to the fragment type CLAC is performed by cleavagebetween amino acid 112 (Arg) and amino acid 113 (Glu) of SEQ ID NO: 2.Therefore, amino acid 113 (Glu) to amino acid 654 (Lys) is the aminoacid sequence of CLAC. Usually, the first amino acid Glu of CLAC iscyclized to be pyroglutamic acid residue.

CLAC-P is converted to CLAC by actions of processing enzymes in thebody. Such processing enzymes are included in the present invention.Such processing enzymes can be identified, for example by any one of thefollowing methods:

(i) For CLAC secreted or produced by cultured cells expressing CLAC-P,the culture broth or extracellular matrix produced around the cells isobtained, and subjected to amino acid analysis, then the cleaved site isdetermined by comparing with CLAC-P, or

(ii) Known protease inhibitor is added to cells expressing CLAC-P, andthe amount of CLAC protein produced in the culture broth or in theextracellular matrix is analyzed, using the decrease in the amount ofCLAC protein as an indicator, or

(iii) Mutation is introduced in the nucleotide sequence of CLAC-P geneto alter amino acid(s) necessary for cleavage by known protease, and themutated gene is expressed. Then the amount of CLAC protein produced inculture broth or in the extracellular matrix is analyzed, using thedecrease of CLAC protein as an indicator, or

(iv) cDNA encoding known protease is further introduced into culturedcells expressing CLAC-P, and the amount of CLAC protein produced in theculture broth or the extracellular matrix is analyzed, using theincrease of CLAC protein as an indicator, or

(v) cDNA encoding CLAC-P is expressed in cultured cells lacking knownprotease, and cultured. Then the amount of CLAC protein produced inculture broth or in the extracellular matrix is analyzed, using thedecrease of CLAC protein as an indicator.

Processing enzymes identified by the methods above mentioned include,but not limited to furin convertase enzyme.

Inhibitors of the proteases include, but not limited todecanoyl-RVKR-chloromethylketone which is a competitive inhibitor offurin convertase and analogous compounds thereof. Cultured cellsexpressing CLAC-P is useful in an effective and sensitive screening ofsubstances that inhibit production or secretion of CLAC because thecultured cells expressing CLAC-P produce and secrete much CLAC.Screening of such substances can be performed, for example by culturingthe transformed cells of the present invention in a medium containing atest substance, and detecting or quantifying the inhibition of CLACproduction or secretion. In said screening method, changes in CLACproduction or secretion from the cells by the test substance can bedetected and quantified, by appropriate methods such as Western blottingmethod using an antibody specific to CLAC.

Specifically, for example, the transformed cells of the presentinvention are plated into multi-well plates, and the cells are culturedin a DMEM medium containing serum to be confluent. After the culturedcells are washed in a serum-free medium (DMEM containing 0.5% bovineserum albumin), a test substance is added to the same medium, and cellsare cultured for a certain period (for example 24 hours). The amount ofCLAC contained in the culture supernatant or in the extracellular matrixattached on the multi-well plate is quantified by Western blottingmethod. Inhibitory effect of the test substance on CLAC productionand/or secretion is estimated by the amount of CLAC compared with thatof the group without the test substance, or by the concentration of thetest substance to induce decrease of CLAC production and/or secretion.

Because the transformed cells of the present invention can besubcultured, and can produce or secrete much CLAC-P and/or CLAC, theycan be used in screening with high efficacy and high reproducibility.Therefore the transformed cells can be advantageously used to screensubstances that inhibit CLAC production or secretion. Moreover a greatamount of stable cloned cells can be always obtained, which makesscreening more stable and effective. Substances identified by suchscreenings that inhibit CLAC production and secretion are included inthe present invention.

A large amount of CLAC can be expressed in cultured cells and purified,for example by, but not limited to following methods (i), (ii), or(iii):

(i) HEK293 cells (ATCC CRL-1573) stably expressing CLAC-P are culturedin DMEM medium containing 10% FBS for 3 days, then when the cells reachto semi-confluency, the cells are cultured in DMEM not containing FBSfor 48 hours, then the culture liquid is recovered. The culture liquidis dialyzed against 50 mM Tris-HCl (pH 8.6) at 4° C. overnight,thereafter centrifuged at 250,000×g for 30 minutes. The precipitate isdissolved in 0.1 M acetic acid, and applied to a DEAE column. Stepwiseelution is performed with 0 M to 1 M NaCl (0.1 M increment). Allfractions are dialyzed against 0.1 M acetic acid, and identification isperformed for example by immunoblotting using a specific antibody 9D2,then positive fraction is used as purified CLAC fraction (for generalprocedures, see Fichard et al., J. Biol. Chem., 272, 30083 (1997)).

(ii) HEK293 cells stably expressing CLAC-P are cultured in DMEM mediumcontaining 10% FBS for 3 days, and when the cells reach tosemi-confluency, the cells are cultured in DMEM not containing FBS for48 hours, then the culture liquid is recovered. The culture liquid isdialyzed against 50 mM Tris-HCl (pH 8.6) at 4° C. overnight, thereaftercentrifuged at 250,000×g for 30 minutes. The precipitate is dissolved in0.15 M acetic acid, and further dialyzed against 20 mM Na₂HPO₄—NaH₂PO₄(pH7.2) containing 2 M urea (PB/U solution) overnight, thereaftercentrifuged at 250,000×g for 30 minutes, and applied to a heparincolumn. Stepwise elution is performed with 0 M to 1 M NaCl (0.1 Mincrement). All fractions are dialyzed against PB/U, and identificationis performed for example by immunoblotting using a specific antibody9D2, then positive fraction is used as purified CLAC fraction (forgeneral procedures, see Mizuno et al., J. Biol. Chem., 120, 934 (1996)).

Or, (iii) CLAC specific antibody (for example 9D2) (1 mg/ml) ispreviously bound to NHS activated carrier such as Affigel 10 (Bio-Rad)to obtain an antibody column. HEK293 cells permanently expressing CLAC-Pare cultured in DMEM medium containing 10% FBS for 3 days, and when thecells reach to semi-confluency, the cells are cultured in DMEM notcontaining FBS for 48 hours, then the culture liquid is recovered.Proteins in the medium are precipitated with 50% saturated ammoniumsulfate. The precipitated proteins are dissolved in IP buffer (TSIsolution [50 mM Tris (Gibco BRL), 150 mM NaCl (Kanto Kagaku), 0.5 mMDIFP (Wako Junyaku), 0.5 mM PMSF (Boehringer Mannheim), 1 mM EGTA (WakoJunyaku), 1 μg/ml antipain (Sigma), 1 μg/ml leupeptin (Wako Junyaku), 1μg/ml pepstatin (Sigma), 1 μg/ml TLCK (Sigma)] containing 0.5% SDS and0.5% NP-40), filtered by 0.45 μm filter, and applied to the antibodycolumn above described. Elution is performed with 0.2 M glycine-HCl (pH2.6) containing 0.1% Triton X-100. Eluted fraction is used as purifiedCLAC (for general procedures, see Hirako et al., J. Biol. Chem., 273,9711 (1998)).

Therefore, further aspect of the present invention is a method forpurification of CLAC using monoclonal antibody 9D2.

Hybridoma producing monoclonal antibody 9D2 has been deposited toInternational Patent Organism Depositary, National Institute of AdvancedIndustrial Science and Technology (AIST Tsukuba Central 6, 1-1, Higashi1-Chome, Tsukuba-shi, Ibaraki-ken, 305-8566, Japan) under accession No.FERM BP-7437.

Further aspect of the present invention is an antibody which bindsspecifically to CLAC-P or CLAC of the present invention.

Specific antibody to CLAC-P or CLAC can be obtained, for example byfollowing methods:

On the basis of amino acid sequences of CLAC and CLAC-P, peptides suchas following peptides are synthesized:

NC-1: Glu Pro Arg Ser Glu Asp Pro Thr Pro Ala Glu Gln His Cys (aminoacids 14 to 27 of SEQ ID NO: 2) (SEQ ID NO: 3)

NC2-1: Gly Cys Asn His Gly Phe Leu Ser Ala Asp Gln Gln Leu Ile Lys(amino acids 171 to 183 of SEQ ID NO: 2, Gly and Cys are added beforeamino acid 171) (SEQ ID NO: 4)

NC2-2: Cys Lys Gly Glu Gln Gly Asp Gln Gly Pro Arg Met Val Phe Xaa Lys(amino acids 155 to 169 of SEQ ID NO: 2, Cys is added before amino acid155) (Xaa represents hydroxyproline) (SEQ ID NO: 5)

NC3: Asp Tyr Asn Gly Asn Leu His Glu Ala Leu Gln Arg Ile Thr Cys (aminoacids 430 to 443 of SEQ ID NO: 2, Cys is added after amino acid 443)(SEQ ID NO: 6)

NC4: Leu Gly Pro Asp Gly Leu Pro Met Pro Gly Cys Trp Gln Lys (aminoacids 641 to 654 of SEQ ID NO: 2) (SEQ ID NO: 7)

Then, these peptides bound to KLH (keyhole Limpet Hemocyanin) are usedas antigen to immunize rabbits. Antisera are obtained by estimating thereactivity with antigen peptides of sera obtained using ELISA method.Antisera are bound to Affigel to which antigen peptide is bound, andonly specific antigen may be affinity-purified.

The splice variant of the eleventh aspect of the present invention canbe also used as above described.

Antibodies specifically binding to CLAC-P or CLAC of the presentinvention may be polyclonal or monoclonal, preferably monoclonalantibodies. Particularly preferred antibody is 9D2 monoclonal antibodyabove described.

Some of such antibodies specifically bind to CLAC or CLAC-P. Some ofsuch antibodies inhibit actions or functions of CLAC or CLAC-P.Therefore, further aspect of the present invention is a method fordetecting CLAC or CLAC-P using such antibodies. This detection methodmay be applied to diagnosis of Alzheimer's disease. These antibodies canbe labeled with known labels in the art such as radioactive labels (forexample ⁹⁹Tc), fluorescent labels or enzymatic labels. These labeledantibodies may be injected into living animals and scaned the image.Alternatively bindings of these antibodies to CLAC or CLAC-P protein aredetected and quantified in biopsy or autopsy samples.

Thus, further aspect of the present invention is a diagnosis kit forAlzheimer's disease comprising a specific antibody to CLAC or CLAC-Pthat is detectably labeled. The kit components may be directly injectedinto a living human being and scanned the image. The kit components mayalso be reacted with a biopsy or autopsy sample. Preferred antibody ismonoclonal antibody 9D2. Labels include, but not limited to, radioactivelabels (for example ⁹⁹Tc), fluorescent labels or enzymatic labels, whichcan be selected according to method for use, purpose of use, applicationsite, etc. Such labels are well known to a skilled person in the art.The diagnostic kit of the present invention may be composed of separatedvessel containing each component, or composed of several vessels inwhich several components are contained. In general, an appropriateinstruction is appended to the kit.

Still further aspect of the present invention is a method for screeninga inhibitor of CLAC or CLAC-P activity which inhibits actions and/orfunctions of CLAC or CLAC-P. Because such an inhibitor subsequently haveeffects such as inhibition of Aβ accumulation, it can be used as atherapeutic agent of Alzheimer's disease.

Such an inhibitor can be screened using for example the following method(i), (ii) or (iii):

(i) For a substance which influences binding of CLAC to beta-amyloid orpromotion of amyloid aggregation, a test substance is added to syntheticAβ (1-42) peptide and an appropriate amount of CLAC, mixed together, andthe mixture is incubated for 0 to 5 days at room temperature, theninhibition of formation of amyloid fibers that emit fluorescence withthioflavin T is estimated. Alternatively, a test substance isadministered orally, intravenously, or intraventrically to a mousegenerated by mating a transgenic mouse over-expressing human CLAC-P genewith a transgenic mouse over-expressing Alzheimer mutant βAPP gene, orto a transgenic mouse over-expressing Alzheimer mutant βAPP gene. Thendecrease of beta-amyloid plaques in brain is immunohistochemically orbiochemically estimated, by comparing with that in brain of a mouse thathas not been given the test substance.

(ii) For a substance which inhibits binding to beta-amyloid of cells viaCLAC-P, HEK293 cells stably expressing CLAC-P and control cells arecultured, and 10 μM of Aβ (1-42) and a test substance that have beenpreincubated in a test tube for 60 min are added. Then, the mixture isincubated further 60 min, and the amount of Aβ bound to the recoveredcells can be estimated.

(iii) For a substance that inhibits cytotoxicity of Aβ bound to cellsvia CLAC-P, for example, PC12 cells having been differentiated to beneurons by NGF are made to transiently express CLAC-P by lipofectionmethod. Then, Aβ (1-42) and a test substance preincubated for 1 hour areadded, thereafter the cells are TUNEL stained to estimate inhibition ofapoptosis, or increase of living cells is estimated by MTT reagent.

Therefore, further aspect of the present invention is a method forscreening such an inhibitor, comprising using CLAC or CLAC-P.

Such inhibitors include, but not limited to antagonists to CLAC orCLAC-P, polypeptides having similar structures to CLAC or CLAC-P, orother low molecular compounds.

Some antibodies that bind specifically to CLAC or CLAC-P of the presentinvention, inhibit the actions and/or functions of CLAC or CLAC-P.Subsequently these antibodies can inhibit accumulation of Aβ in brain,and treat, retard or prevent Alzheimer's disease.

Thus, another aspect of the present invention is a method to treat,retard or prevent Alzheimer's disease comprising administering such aninhibitor or an antibody. Such an inhibitor or an antibody may beadministered solely or with an appropriate carrier such as purifiedwater or saline. The routes of administration include intravenous routeand intracerebrospinal cavity route, preferably intravenous route. Thedose is normally 1 ug to 100 mg/kg, however the dose can be altereddepending on route of administration, severity of the disease to betreated, condition of the patient, etc.

Suitable antibody to the above-mentioned method is monoclonal antibody9D2.

A substance which has therapeutic effect of Alzheimer's disease byinhibiting production of CLAC or CLAC-P itself, is also included in thepresent invention. An example of the method for screening such asubstance is as follows:

For a substance which has a therapeutic effect via decrease of CLAC orCLAC-P production, screening can be performed by culturing thetransformed cells of the present invention in a medium containing a testsubstance, and detecting or quantifying production or secretion of CLAC.In said screening method, change in production or secretion of CLAC fromcells by the test substance can be detected and quantified, usingsuitable methods such as Western blotting method using an antibodyspecific to CLAC.

Specifically, for example the transformed cells are plated in amulti-well plate, and cultured in DMEM medium containing sera to beconfluent. After the cells are washed in a serum-free medium (DMEMcontaining 0.5% bovine serum albumin), a test substance is added to thesame medium, and cultured for a certain period (for example 24 hours).The amount of CLAC contained in the culture supernatant or in theextracellular matrix is quantified by Western blotting method. And,inhibitory effect of the test substance on CLAC production and/orsecretion is estimated by the amount of CLAC compared with that in thegroup not containing the test substance, or by the concentration of thetest substance to induce decrease of CLAC production and/or secretion.Such a screening method is also included in the present invention.

Further a peptide molecule which interacts with CLAC or CLAC-P and isphysiologically useful, can be identified and/or obtained, for example amethod comprising either step of (i), (ii) or (iii):

(i) A gene library in which a gene of human CLAC-P is fused to a gene ofDNA binding protein and a gene library in which a gene of transcriptionactiviating protein is fused to cDNAs from human brain are expressed inyeast cells, and genes showing positive reactions are obtained by use oftwo hybrid method.

(ii) An extract of human brain is passed to a column to which humanCLAC-P or CLAC recombinant protein is bound, and the bound protein iseluted and submitted to amino acid sequence analysis.

(iii) An extract of human brain is passed to a column to which humanCLAC-P is immobilized, and the protein which binds to the columntogether with human CLAC-P or CLAC is eluted and submitted to amino acidsequence analysis.

Such a peptide molecule is also useful in treatment, retardation orprevention of Alzheimer's disease. Therefore, such a peptide molecule,and a method for identifying and/or obtaining it are also included inthe present invention.

A protein that influences secretion and/or production of CLAC-P and/orCLAC is also useful in a method for treatment, retardation or preventionof the present invention. Such a protein can be identified, for exampleby making cultured cells expressing CLAC-P to express human cDNAlibrary, selecting a clone expressing single cDNA by limiting dilution,and estimating change in the amount of secreted CLAC from the cellclone, then identifying the gene introduced. Therefore, such a protein,and a method for identifying it are also included in the presentinvention.

Further aspect of the present invention is a transgenic animal in whicheither CLAC DNA or CLAC-P DNA is artificially introduced into thechromosome, or either DNA is deleted from the chromosome. A transgenicanimal is an animal in which a foreign gene is introduced by recombinantDNA method. Transgenic animal has a character that is not obtained byusual breeding. A method for producing a transgenic animal is well knownto a skilled person in the art. Generally, transgenic animal can beproduced by a process comprising following steps: cloning a genecontaining a DNA to be introduced, ligating the gene to a promoter whichexpresses in desired organ and at desired time, introducing theconstruct into a fertilized egg, and transplanting the fertilized egginto a pseudopregnant female animal. By suitably selecting or mutatingthe expression regulating sequence, a transgenic animal can be obtainedin which expression of CLAC or CLAC-P of the present invention isartificially regulated. Knockout animal is also included in transgenicanimal. Such transgenic animals are useful in regulation of functions orexpression of CLAC or CLAC-P of the present invention, investigation ofdevelopment of diseases in which CLAC or CLAC-P involves, screening anddevelopment of medicines, etc. Preferably such transgenic animals arethose other than a human being.

CLAC-P and CLAC from other animals than a human being can be cloned. Forexample, using cDNA library from desired animal, by amplifying a gene ina similar method to above mentioned, genes of CLAC-P and CLAC of desiredanimal can be cloned, and amino acid sequences thereof can be deduced(for cloning of mouse CLAC-P gene, see Example 7 of the specification).

EXAMPLES

The present invention is described by reference of the Examples below.The Examples should not be construed to limit the present invention.

Example 1 Preparation of Monoclonal Antibody 9D2

(1) Partial Purification of Senile Plaque Amyloid

Gray matter was cut out of Alzheimer's brain cortex, homogenized with apotter homogenizer (Matsushita Electric Industrial) in TSI solutioncontaining 1 M sucrose (Kanto Chemicals) [50 mM Tris (Gibco BRL), 150 mMNaCl (Kanto Chemicals), 0.5 mM DIFP (Wako Pure Chemical Industries,Ltd.), 0.5 mM PMSF (Boehringer Mannheim), 1 mM EGTA (Wako Pure ChemicalIndustries, Ltd.), 1 μg/ml antipain (Sigma), 1 μg/ml leupeptin (WakoPure Chemical Industries, Ltd.), 1 μg/ml pepstatin (Sigma), 1 μg/ml TLCK(Sigma)], and centrifuged at 260,000×g in a centrifuge (Hitachi Koki) at4° C. for 30 min.

The Pellet obtained was suspended in TSI solution supplemented with 1Msucrose, and fractionated by discontinuous sucrose density gradientcentrifugation (Am. J. Pathol., 148 1517 (1996)) to collect 1.5Msucrose/2.2M sucrose interface.

The interface collected was treated with DNase I (Wako Junyaku) at 37°C. for 3 hours, and suspended into TSI solution containing 1% Triton-X100 and 5M urea (Nacalai Tesque), and capillaries were removed (J.Neurochem., 58 1953 (1992)), and centrifuged (100,000×g) in acenterifuge at 4° C. for 30 min.

Pellets obtained were used as an amyloid fraction.

(2) Preparation of Antibodies

The senile plaque amyloid fraction was suspended into a 50 mM Trissolution containing 1% SDS, emulsified with a Freund's complete adjuvant(Sigma), and inoculated to mouse's foodpad (BALB-C, 7 weeks, male) [J.Exp. Med., 169 1693 (1989)].

After 25 days from immunization, lymph nodes of posterior limbs wereremoved, and lymphocytes were taken out in RPMI medium. The lymphocyteswere fused to myeloma cells (PAI strain) from mouse myeloma, andhybridomas were prepared. The hybridomas were suspended in HAT medium,and dispersed into 96-well plates (Greiner) and cultured for 10 days.

(3) Screening of Monoclonal Antibodies

Hybridoma supernatants were collected from wells, and antibodies thatstain amyloid positively were selected on smears of senile plaqueamyloid fraction (Am. J. Pathol., 148 1517 (1996)).

From 288 hybridoma clones, most positive monoclonal antibody 9D2 wasselected. Isotype of the monoclonal antibody was identified as IgG1 byuse of Mouse antibody isotype kit (Amersham). A hybridoma that producethe highest amount of 9D2 antibody was designated as hybridoma 9D2, anddeposited to International Patent Organism Depositary, NationalInstitute of Advanced Industrial Science and Technology (AIST TsukubaCentral 6, 1-1, Higashi 1-Chome, Tsukuba-shi, Ibaraki-ken, 305-8566,Japan) and assigned an accession No. FERM BP-7437 on Jan. 30, 2001.

Surprisingly it was found that such antibodies bound strongly andspecifically to unknown proteins (referred as CLAC-P and CLAC in thisspecification) from Alzheimer's brain. In particular, monoclonalantibody 9D2 binds very strongly and specifically to CLAC-P and CLAC.Moreover monoclonal antibody 9D2 is characterized in that it stronglyreacts with a peptide fragment Xaa Ala Pro Ser Glu Cys (SEQ ID NO: 29)in which amino acid 113 Glu of CLAC-P is changed to pyroglutamic acid.

Cloning, sequencing, etc of these genes encoding these unknown proteins(i.e. CLAC-P and CLAC) are described in Example 2.

Example 2 Cloning of Human CLAC-P Gene

Twenty grams of Gray matter was cut out of Alzheimer's cerebral cortex,homogenized with a potter homogenizer in TSI solution, and centrifugedat 260,000×g in a centrifuge at 4° C. for 20 min. Pellets obtained wassuspended in TSI solution supplemented with 1M sucrose, and centrifugedat 260,000×g in a centrifuge at 4° C. for 20 min. Pellets obtained weresuspended into TSI solution containing 0.32M sucrose, and capillarieswere removed, and centrifuged at 260,000×g in a centrifuge at 4° C. for20 min. Pellets obtained were homogenized in TSI solution containing 2%SDS (Nacalai Tesque) using a homogenizer, and centrifuged at 260,000×gin a centrifuge at 4° C. for 20 min. Pellets obtained were broken in 70%formic acid (Wako Pure Chemical Industries, Ltd.) by a sonicator(Branson), and centrifuged at 260,000×g in a centrifuge at 4° C. for 20min. The supernatant was freeze-dried in a freeze-drier (Tomy),thereafter suspended in an aqueous solution of 6M guanidinehydrochloride (Nacalai Tesque), and centrifuged at 260,000×g in acentrifuge at 4° C. for 20 min. 70% formic acid ( 1/100 volume of thesupernatant) was added, and separated by RP-HPLC (Hewlett-Packard) usingAquapore RP300 column (2.1×30 mm, Applied Biosystems)[J. Biol. Chem.,267 17047 (1992)].

A fraction positive for monoclonal antibody 9D2 was selected byimmunoblotting method using SDS-PAGE (Proc. Natl. Acad. Sci. USA, 942025 (1997)), and it was found that the fraction was eluted with ca. 30%acetonitrile (Wako Pure Chemical Industries, Ltd.). After the fractionpositive for 9D2 was freeze-dried, the fraction was suspended in 6 Mguanidine hydrochloride aqueous solution, reduced by reductivecarboxy-methylation method (J. Biol. Chem., 238 622 (1963)), andseparated by gel-filtration HPLC using TSKgel SuperSW3000 column(4.6×600 mm, Tosoh). A fraction of ca. 35 kDa to which 9D2 antibodystrongly reacted in immunoblotting method was digested with a lysylendopeptidase API (achromobacter lyticus protease I), or Asp-N(Boehringer Mannheim)[J. Biol. Chem., 267 17047 (1992)]. Digests wereseparated by RP-HPLC using Superspher Select B column (2.1×125 mm,Merck) to obtain a peptide map.

A fraction obtained by peptide map was analyzed by a TOF (time offlight) type mass spectrometer (Bruker-Franzen Analytik) and an aminoacid sequencer (Applied Biosystems)[J. Biol. Chem., 274 7368 (1999)],and partial amino acid sequences were selected that had identicalmolecular weights to those obtained by the mass spectrometer.

Sequences obtained are as follows (upper: amino terminal; bottom:carboxy terminal):

By digestion enzyme API

Ile Asn His Gly Phe Leu Ser Ala Asp Gln Gln Leu Ile Lys (SEQ ID NO: 8),and

Gly Glu Gln Gly Asp Gln Gly Hyp Arg Met Val Phe Pro Lys (SEQ ID NO:9)

were obtained (Hyp represents hydroxyproline).

By digestion enzyme Asp-N

Asp Gln Gly Pro Arg Met Val Phe Pro Lys Ile Asn His Gly Phe Leu Ser Ala(SEQ ID NO: 10)

was obtained.

As a result, following amino acid sequence of 28 amino acids wasobtained as a partial amino acid sequence of 9D2 antigen:

Gly Glu Gln Gly Asp Gln Gly Pro Arg Met Val Phe Pro Lys Ile Asn His GlyPhe Leu Ser Ala Asp Gln Gln Leu Ile Lys (SEQ ID NO: 11)

On the basis of this sequence, cDNA of 9D2 antigen portion was cloned byPCR (polymerase chain reaction) method using degenerated primers. Theprimers used were designed as follows:

5′-aar ggi gar car ggi gay car ggi cc-3′ (SEQ ID NO:12)

5′-agc tgc tgr tci gcd gav agr aab cc-3′ (SEQ ID NO: 13)

5′-agc tgc tgr tci gcr ctv agr aab cc-3′ (SEQ ID NO: 14)

wherein i represents inosine, r represents a or g; y represents c or t;d represents a, g or t; and v represents a, g or c.

Using Human brain Marathon-Ready cDNA Library (CLONTECH) as a template,a 80 bp cDNA fragment was amplified by LA Taq (TaKaRa) in a PCRapparatus (TaKaRa)—40 cycles of: heat denaturation at 95° C. for 30 sec,annealing at 58° C. for 30 sec, and DNA synthesis at 72° C. for 1 min.This fragment was sub-cloned into pBluescript II KS+ (Stratagene), andsequenced by an automatic sequencer (Li-COR) using Thermo sequencing kit(Amersham).

By repeating RACE method using PCR based on the sequence of thefragment, cloning of CLAC-P DNA was performed that included ORF (openreading frame) of CLAC-P. Specific primers used are as follows:

5′-tag ctg ctg gtc ggc gct gag gaa gcc a-3′ (SEQ ID NO:15)

5′-aag ggg gaa cag ggg gac cag ggg ccg a-3′ (SEQ ID NO:16)

5′-tcg gaa aca cca tcc tcg gcc cct ggt c-3′ (SEQ ID NO:17)

5′-cat ggc ttc ctc agc gcc gac cag cag c-3′ (SEQ ID NO:18)

5′-cgc cgc ctg att aag ggt gac caa gga c-3 (SEQ ID NO:19)

5′-aag agg gcc acc tgg gga cac agg gaa a-3′ (SEQ ID NO:20)

5′-acc ctt ggg gcc gtt ctc tcc agc gtc t-3′ (SEQ ID NO:21)

5′-cac ctt gtt ctc cag gtt ctc cct tag g-3′ (SEQ ID NO:22)

5′-gaa tac cag gac cta agg gag aac ctg g-3′ (SEQ ID NO:23)

5′-ggc ccc aag ggt gac aca ggc gaa aag g-3′ (SEQ ID NO:24)

5′-ccc tcc ttt ccc tgc gtg ctt ctt cag c-3′ (SEQ ID NO:25)

5′-tct cgg ctt cgc ttc cca ccc tct aca c-3′ (SEQ ID NO:26)

5′-gga gat tct gga atg ccg ggt cca cag g-3′ (SEQ ID NO:27)

5′ ctt cta tca tag gcc cac cag gcc cac c-3′ (SEQ ID NO:28)

The fragment was amplified by LA Taq (TaKaRa) in PCR apparatus (TaKaRa)using Human brain Marathon-Ready cDNA Library (CLONTECH) as atemplate—35 cycles of: heat denaturation at 95° C. for 30 sec, annealingat 58° C. for 1 min, and DNA synthesis at 72° C. for 5 min, thereafternested primer added—30 cycles of: heat denaturation at 95° C. for 30sec, annealing at 60° C. for 1 min, and DNA synthesis at 72° C. for 5min. The fragment obtained was sub-cloned into pBluescript II KS+, andsequenced by an automatic sequencer using Thermo sequencing kit.

Thus, cDNA of novel protein CLAC-P was obtained (SEQ ID NO: 1). Theamino acid sequence of the ORF (SEQ ID NO: 2) was deduced from thenucleotide sequence. These DNA and amino acid sequences are shown inFIG. 1.

cDNA of CLAC-P contains an ORF encoding 654 amino acids in length (FIG.1, SEQ ID NO: 1, and SEQ ID NO: 2). CLAC-P is a novel protein that istype II single pass transmembrane protein. Its amino terminal is locatedon the cytoplasmic side, and its carboxy terminal is on theextracellular side. The amino acid sequence has three repeats ofcollagen-like Gly-Xaa₁-Xaa₂ (G represents glycine; Xaa₁ and Xaa₂represent any amino acids) in the extracellular region. mRNA expressionwas investigated in various human tissues using RT-PCR method, andspecific expression was found in brain and testis. A peptide antibodyprepared on the basis of the deduced amino acid sequence stained senileplaques in Alzheimer's brain, and it was found that the protein fragmentderived from the cDNA obtained accumulated in senile plaque amyloid.

Example 3 Assay of Amyloid Beta Peptide Receptor Function of CLAC-PUsing Human Transformed Cells that Permanently Express Human CLAC-P

A plasmid DNA in which CLAC-P gene was integrated was prepared asdescribed below: CLAC-P gene was altered to be cleaved at position −40of 5′ UTR region of CLAC-P by HindIII, and at position +100 from thefirst stop codon of the 3′ UTR region. The altered CLAC-P gene wasintegrated into HindIII-BamHI region of multicloning site ofpcDNA3.1/Hygro(+) (invitrogen) having CMV promoter.

HEK293 cells were plated into 6-well plates (Nunc) at a concentration of3.0-5.0×10⁵ cells/well, and cultured for 24 hours. Then, solution A: 1ug plasmid DNA/100 μl Opti-MEM (Gibco BRL) and solution B: 10 μlLipofectAMINE (Gibco BRL)/100 μl Opti-MEM are prepared, mixed togetherand incubated for 30 min, then 800 μl of Opti-MEM was added to themixture to 1 ml (DNA-Lipofectamine complex) (per well). DMEM was removedfrom the cells, and the cells was washed with Opti-MEM (1×), then 1 mlof DNA-Lipofectamine complex was added to each well and cultured for 6hours. Then 1 ml of DMEM containing 20% FBS was added, and cultured forfurther 24 hours. After replacement of the medium to DMEM, cultured forfurther 24 hours. Thereafter the cells in each well were re-plated into10 cm dish, and selection culture was performed in DMEM containing 133μg/ml of hygromycin (Wako Junyaku). After selection culture for 10-14days, grown cells are taken as polyclonal cell strains in which desiredplasmid was introduced. Polyclonal cell strains were further cloned bylimited dilution method, and 15 monoclonal cell strains were obtained.The monoclonal cell strains were analyzed for their expression byimmunoblotting using an antibody specific to CLAC-P protein. Threestrains that showed maximum expression were selected, designated as9D2-1, 9D2-2, and 9D2-11, and used subsequent experiments. Strain 9D2-1which was a transformant of HEK293 cell permanently expressing humanCLAC-P was deposit to International Patent Organism Depositary, NationalInstitute of Advanced Industrial Science and Technology (AIST TsukubaCentral 6, 1-1, Higashi 1-Chome, Tsukuba-shi, Ibaraki-ken, 305-8566,Japan) and assigned an accession No. FERM BP-7438 on Jan. 30, 2001.

Cover glasses pre-coated with poly-L-lysine (Sigma, 10 ug/ml) werearranged on 10 cm dishes, upon which cells were applied, cultured,gene-introduced, and recovered the cover glasses. The cover glasses werewashed with PBS solution (2×), then fixed with PBS solution containing4% paraformaldehyde (TAAB) at room temperature for 30 min. After furtherwashing with PBS solution (2×), permeabilization and blocking wereperformed with PBS solution containing 0.5% Triton X-100, 0.3% BSA(Bovine serum albumin, Sigma) at room temperature for 30 min. Thesolution was removed, and an antibody was added which was diluted (1/1000) with PBS solution containing 0.3% BSA, and reacted at roomtemperature for 2 hours. After washing with PBS (3×),FITC-bound-anti-rabbit antibody (Jackson) as a secondary antibody wasadded which was diluted with PBS solution containing 0.3% BSA, thenreacted at room temperature for 1 hour with glare protection. Afterwashing with PBS (3×), the sample was encapsulated with a encapsulatingagent and observed using a fluorescent microscope. (AX-80, Olympus).Distribution of CLAC-P was observed in cell membrane system,particularly endoplasmic reticulum, Golgi apparatus and cell surfacemembrane.

After monoclonal HEK293 strain stably expressing CLAC-P cultured in 10cm dish was washed in TS solution, the strain was recovered bycell-scraper in TSI solution. The cells were disrupted in a polytronhomogenizer (Hitachi Koki), then centrifuged at 1,000×g, 4° C., for 7min. The supernatant was collected, and centrifuged at 2,000×g, 4° C.,for 30 min. The pellet was used as a mitochondria and lysosome fraction.The supernatant was further ultra-centrifuged at 100,000×g, 4° C., for60 min. The pellet was recovered as a microsome fraction and analyzed,and the supernatant was recovered as cytoplasmic fraction and analyzed.As shown in right panel (B) of FIG. 2, expression of a full lengthCLAC-P protein of 80 kDa was detected specifically in membrane fractionof CLAC-P expressing cells.

HEK293 cells permanently expressing human CLAC-P, and control cellspermanently expressing pcDNA3.1 vector only were cultured in 10 cmdishes, and when reached to confluent, 10 μM Aβ (1-42) (Bachem)preincubated at 37° C. for 60 min was added, and incubated for a certainperiod. After incubation, culture supernatant containing Aβ was removed,and the cells were washed in PBS (3×), then collected by a scraper, andprecipitated in a microcentrifuge (TOMY) at 7,000 rpm for 5 min. Samplebuffer was added to the cell pellet, and solubilized by sonication, andthe protein was quantified using BCA protein assay kit (Piearce).

The amounts of the proteins contained each sample were adjusted to be acertain level, and 2-mercaptoethanol was added (final concentration was1%), and heated for 10 min. The proteins were separated by SDS-PAGEusing 15% Tris-Tricine gel, and transferred to a nitrocellulose membrane(Hybon-ECL, Amersham) under a condition of 3 hours at 150 mA.Transferred membrane was heated in PBS for 10 min, then blocked in 1%skim milk (Difco)-PBS at room temperature for 30 min, and reacted withvarious antibodies diluted by similar blocking solution at roomtemperature for 2 hours, or at 4° C. overnight. The membrane was reactedsolution at room temperature for 1 hour with a secondary antibody(anti-mouse or anti-rabbit Ig, horseradish peroxdase bound wholeantibody (Amersham)) that were washed in PBS-T (PBS containing 0.1%Tween 20) for 10 min (3×), then diluted with similar blocking. Afterwashing in PBS-T for 10 min (3×), exposed to Hyperfilm-ECL (Amersham)using ECL kit (Amersham), and Aβ binding was detected. Cells expressinghuman CLAC-P bound 30 ng of Aβ (1-42) per mg protein, while cellsexpressing the vector only bound 6 ng of Aβ. As the result of aboveexperiment, binding of Aβ increased five times, which indicated thathuman CLAC-P expressed on cell surface acts as a receptor for Aβ.

Example 4 Amino Acid Sequence of CLAC from Amyloid in Human Alzheimer'sBrain, and the Reactivity with 9D2 Antibody

CLAC purified from human Alzheimer's brain according to the method of(1) described in Example 2, was subjected to amino acid analysis,however it was impossible to analyze the protein because the aminoterminal was blocked. A peptide corresponding to amino acids 113-118 ofCLAC-P, Xaa Ala Pro Ser Glu Cys (SEQ ID NO: 29) was synthesized in whichamino acid 113 Glu was substituted with pyroglutamic acid (Xaa). Thepeptide was bound to KLH through Cys residue, then the bound peptide wasused as an immunogen to produce an antibody (hereinafter, said antibodyis referred as PyroG). As inferred from the description of Neuron, 14457 (1995), antigen PyroG specifically recognized the structure of theamino terminal opposite to the KLH binding side of the synthesizedpeptide. Namely, PyroG did not react with full length recombinant CLAC-Pprotein obtained by expression in cultured cells according to the methodof Example 3 when immunoblotting method was performed using SDS-PAGE.However, Xaa Ala Pro Ser Glu Cys (SEQ ID NO: 29) peptide was immobilizedto a micro-well plate (according to the method of EMBO J., 11, 2895(1992)), and enzyme-linked immunosorbent assay (ELISA) was performed byindirect peroxidase method using PyroG antibody as a primary antibody.In the ELISA, positive reaction was found. Also, CLAC obtained fromhuman Alzheimer's brain as above described reacted positively with PyroGin immunoblotting method. Further, positive reaction of 9D2 antibody andCLAC from Alzheimer's brain in immunoblotting method, andimmunohistochemical staining with Alzheimer's brain tissue specimen werediminished by preliminary mixing Xaa Ala Pro Ser Glu Cys (SEQ ID NO: 29)with 9D2 antibody to absorb the antibody activity (according to Neuron,13, 45 (1994)). These facts indicated that CLAC from Alzheimer's brainamyloid starts from amino acid 113 of CLAC-P and the amino acid 113 ispyroglutamic acid and that 9D2 antibody recognizes CLAC proteinunderwent such a modification.

Example 5 In Vitro Binding of CLAC to Beta-Amyloid (Aβ)

In vitro binding of CLAC to Aβ was performed according to a method ofWebster et al. (Am. J. Pathol., 150, 1531 (1997)).

The transformant (strain 9D2-1) permanently expressing human CLAC-Pobtained in Example 3 was selection-cultured in DMEM medium containing10% FBS and hygromycin for 4 days, and the culture supernatant wascollected. Fifty μl (0.1 mg/ml) of synthetic Aβ (1-42) (Bachem) wasimmobilized to each well of 96-well micro-well plates (Greiner), anddried in a desiccator. Thereafter, blocking was performed with PBS-Tcontaining 1% gelatin (Wako Junyaku) for 1 hour, and washed with PBS-Tfor 10 min (3×), and the culture supernatant obtained was applied.Similarly, culture supernatant of control HEK293 cells used in Example 3was applied. After reaction at room temperature for 1 hour, washed withPBS-T for 10 min (5×), and then reacted with anti-CLAC antibody dilutedwith similar blocking solution ( 1/5000) at room temperature for 1 hour.After washing with PBS-T for 10 min (5×), reacted with a secondaryantibody (anti-rabbit Ig, horseradish peroxidase bound whole antibody(Amersham)) diluted with similar blocking solution ( 1/5000) at roomtemperature for 1 hour. After washing with PBS-T for 10 min (5×), colourwas developed with TMB reagent (Kirkegard & Perry Laboratories).

As a result of ten trials, the culture supernatant of transformantpermanently expressing CLAC-P that secretes CLAC developed strongercolour about fifty times than control HEK293 that does not secrete CLAC,which indicates that CLAC significantly binds to Aβ (p<0.0001) in vitro.

Example 6 Effects of CLAC on Aβ Aggregation

The transformant (strain 9D2-1) permanently expressing human CLAC-Pobtained in Example 3 was selection-cultured in DMEM medium containinghygromycin and 10% FBS for 3 days, and cultured starting fromsemi-confluency for 4 days in DMEM not containing FBS, and then theculture supernatant was collected. After centrifugation at 2,000×g, thesupernatant was applied to a DEAE column (Whatman), and the through-passfraction was further applied to a heparin column (Amersham). Afterwashing the column fully with PBS solution containing 2M urea (NacalaiTesque) (PB-U solution), elution was performed with PB-U solutioncontaining 1M NaCl, and the eluate was dialyzed against PBS solution.The solution thus obtained was used as crude purified CLAC, and thesolution obtained from control HEK293 cells was used as a control.

Experiment of Aβ aggregation was performed according to the standardmethod of LeVine (Methods in Enzymology, 309, 274).

One hundred μl of the crude purified CLAC or the solution from controlHEK293 cells was added to 3.6 μM synthesized Aβ (1-42) (Bachem), andafter passing through 0.22 μM filter, reacted at 37° C. for 1 day. Fourhundred μl of glycine-NaOH solution (10 μM, pH=8.5) containing 3 μMthioflavin T was added to the reaction mixture, and the fluorescence wasmeasured in a fluorophotometer (Hitachi F-2000) (excitation at 442 nm;measurement at 496 nm).

By eighteen trials, it was shown that Aβ aggregated with the crudepurified CLAC sixty times as much as with the solution from the controlHEK293 cells, and this result was significant (p<0.0001).

Example 7 Cloning of Mouse CLAC-P cDNA

Mouse brain Marathon-Ready cDNA Library (CLONTECH) was used as atemplate, mouse CLAC-P cDNA was cloned by PCR method. Following primerswere prepared based on human CLAC-P cDNA sequence:

5′-GGG ATC AAG GAG CCA CTA AGA TCA TAG A-3′ primer 1 (SEQ ID NO: 30)

5′-GGG CCT ATG ATA GAA GGA CCC TGT GGA C-3′ primer 2 (SEQ ID NO: 31)

5′-CTA CAA CGG CAA CCT CCA CGA AGC CTT-3′ primer 3 (SEQ ID NO: 32)

5′-TCT CCC TTT ATC CCC GGA AGT C-3′ Primer 4 (SEQ ID NO: 33)

Using primers 1 and 2, a cDNA fragment of about 330 bp was amplified byPCR apparatus (TaKaRa) using PremixLATaq (TaKaRa)—40 cycles of: heatdenaturation at 95° C. for 45 sec, annealing at 42° C. for 45 sec, DNAsynthesis at 72° C. for 3 min. Then, the reaction mixture as a templatewas added to PremixLATaq (1:50), and using primers 2 and 3, nested PCRwas performed—35 cycles of: heat denaturation at 95° C. for 45 sec,annealing at 51° C. for 45 sec, DNA synthesis at 72° C. for 3 min. Thus,a fragment of about 300 bp was obtained. This fragment was purified, andsub-cloned into pBluescript II KS+ (Stratagene) by TA cloning method,and sequenced using an automatic sequencer (Li-COR) (SEQ ID NO: 50).

By searching on the basis of human CLAC-P, a sequence of about 70 bpfrom adult mouse testis was found in GenBank (AV264752, SEQ ID NO: 51)that has a high homology to human CLAC-P. Based on this sequence and thesequences previously obtained, new primers were synthesized:

5′-CGA ATA TAT GGC TAA AAT AAG AAC GGT C-3′ primer 5 (SEQ ID NO: 34)

5′-CTG GCA AAC CGG TGT CTC CTT TCT CTC-3′ primer 6 (SEQ ID NO: 35)

5′-ACG GTC AGG GAG GCA CCT TTA GAG TGC A-3′ primer 7 (SEQ ID NO: 36)

5′-CTC TCC TTT TAC TCC ATT GGC ACC CGG C-3′ primer 8 (SEQ ID NO: 37)

5′-ACG GTC AGG GAG GAA GCT TTA GAG TGC A-3′ primer 9 (SEQ ID NO: 38)

5′-TCA ACT CCG GGG ATC CCT GGA GAG CCT T-3′ primer 10 (SEQ ID NO: 39)

Firstly, using primers 5 and 6, PCR reaction was performed—38 cycles of:heat denaturation at 95° C. for 45 sec, annealing at 55° C. for 45 sec,DNA synthesis at 72° C. for 3 min. Using this reaction mixture as atemplate, and using primers 7 and 8, PCR was performed in sameconditions to amplify a fragment of about 1200 bp. The fragment waspurified, and using primer 4 synthesized as a dye-primer, the nucleotidesequence was analysed by an automatic sequencer. Based on thisnucleotide sequence, the following primers were prepared:

5′-GGG ACC ATT TTC TCG AGC ATC TCC CTT T-3′ primer 11 (SEQ ID NO: 40)

5′-AAA ATG GTC CCA AAG GTG ATA CAG GAG-3′ primer 12 (SEQ ID NO: 41)

Using the reaction mixture obtained by PCR using primers 5 and 6 as atemplate, and using primers 9 and 11, PCR reaction was performed—38cycles of: heat denaturation at 95° C. for 45 sec, annealing at 56° C.for 45 sec, DNA synthesis at 72° C. for 3 min. A fragment of about 560bp thus obtained was digested with XhoI and HindIII. A XhoI-HindIIIfragment was sub-cloned into pBluescript II KS+, and the nucleotidesequence was identified (SEQ ID NO: 52). Also, using the reactionmixture obtained by PCR using primers 5 and 6 as a template, and usingprimers 10 and 12, PCR reaction was performed—38 cycles of: heatdenaturation at 95° C. for 45 sec, annealing at 56° C. for 45 sec, DNAsynthesis at 72° C. for 3 min. A fragment of about 550 bp thus obtainedwas digested with XhoI and HindIII. A XhoI-HindIII fragment wassub-cloned into pBluescript II KS+TA cloning method, and the nucleotidesequence was identified (SEQ ID NO: 53).

Next, RACE (rapid amplification of cDNA ends) method was performed onthe basis of these sequences. Following primers were used:

5′-TGC ACT CTA AAG GTG CCT CCC TGA CCG T-3′ primer 13 (SEQ ID NO: 42)

5′-GAC CGT TCT TAT TTT AGC CAT ATA TTC G-3′ primer 14 (SEQ ID NO: 43)

5′-TGG TAA CCT CCA TGA GGC CTT ACA GAG A-3′ primer 15 (SEQ ID NO: 44)

5′-GAG AGA AAG GAG ACA CCG GTT TGC CAG-3′ primer 16 (SEQ ID NO: 45)

5′-GGC TGG ATG CTC CTT GCC AAT TGG GA-3′ primer 17 (SEQ ID NO: 45)

5′-TGG GAC CTG ATG GGT TAC CTA TGC CTG-3′ primer 18 (SEQ ID NO: 46)

Using mouse brain Marathon-Ready cDNA Library (CLONTECH) as a template,PCR reaction was carried out—cycles of heat denaturation at 95° C. for45 sec, annealing at 59° C. for 45 sec, DNA synthesis at 72° C. for 5min were repeated. Nested PCR was applied to the reaction mixture—cyclesof heat denaturation at 95° C. for 45 sec, annealing at 60° C. for 45sec, DNA synthesis at 72° C. for 5 min were repeated to amplify afragment. The fragment was sub-cloned into pBluescript II KS+ by TAcloning method, and the nucleotide sequence was identified (SEQ ID NOs:54, 55 and 56).

From these DNA fragments, the sequence of mouse CLAC-P cDNA wasdetermined (FIG. 3 and SEQ ID NO: 48). From this cDNA sequence, theamino acid sequence of the ORF was deduced (FIG. 4 and SEQ ID NO: 49).Mouse CLAC-P cDNA encoded 666 amino acids (full length). Its homology tohuman CLAC-P cDNA was about 83%, and about 90% at amino acid level. Themolecular structure of mouse CLAC-P was basically the same as humanCLAC-P, and it was type II single pass transmembrane protein, and hadthree collagen-like repeat in the extracellular region. Moreover withinthe collagen-like sequence, a sequence that undergoes alternativesplicing (FIG. 4, underlined; SEQ ID NO: 49) was identified.

PROBABILITY OF INDUSTRIAL USE OF THE INVENTION

Novel collagen-like protein CLAC obtained in the present inventionaccumulates in Alzheimer's senile plaque amyloid, and promotesaggregation of beta-amyloid that is the main component of Alzheimer'ssenile plaque amyloid. CLAC-P, a precursor of CLAC, is distributed onthe surface of cell membrane as a transmembrane protein, and acts as areceptor that binds beta-amyloid to the cell surface. Thus CLAC-P isinvolved in the progress of Alzheimer's disease. CLAC-P can be useful inprevention, retardation and treatment of Alzheimer's disease.

SEQUENCE LISTING FREE TEXT

SEQ ID NO: 5

Xaa is hydroxyproline.

SEQ ID NO: 9

Xaa is hydroxyproline.

SEQ ID NO: 12

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

r is g or a. i is inosine. y is t or c.

SEQ ID NO: 13

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

r is g or a. i is inosine. v is a, g or c. d is a, g or t.

SEQ ID NO: 14

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

r is g or a. i is inosine. v is a, g or c.

SEQ ID NO: 15

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 16

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 17

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 18

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 19

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 20

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 21

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 22

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 23

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 24

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 25

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 26

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 27

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 28

Designed oligonucleotide primer to amplify human CLAC-P cDNA fragment.

SEQ ID NO: 29

Xaa is pyroglutamic acid.

SEQ ID NO: 30

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 31

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 32

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 33

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 34

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 35

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 36

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 37

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 38

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 39

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 40

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 41

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 42

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 43

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 44

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 45

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 46

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

SEQ ID NO: 47

Designed oligonucleotide primer to amplify mouse CLAC-P DNA fragment.

1. An isolated polynucleotide comprising the nucleotide sequence ofnucleotides 868 to 2493 of SEQ ID NO: 1; wherein said polynucleotideencodes a protein having the following properties: (a) accumulating insenile plaque amyloid component of Alzheimer's disease, and (b) having afunction of promoting aggregation of Aβ.
 2. An isolated polynucleotidecomprising the nucleotide sequence of nucleotides 532 to 2493 of SEQ IDNO: 1; wherein said isolated polynucleotide encodes a proteinfunctioning as an Aβ receptor on cell surface.
 3. An isolatedpolynucleotide comprising a nucleotide sequence encoding amino acids 113to 654 of SEQ ID NO:2.
 4. The isolated polynucleotide of claim 3,wherein said polynucleotide is an expression vector.
 5. The isolatedpolynucleotide of claim 3, comprising a promoter upstream of saidnucleotide sequence for expression thereof.
 6. The isolatedpolynucleotide of claim 5, wherein said promoter is a SV40 promoter, aCMV promoter, or a retroviral promoter.
 7. An isolated cell comprisingthe isolated polynucleotide of claim
 3. 8. An isolated polynucleotidecomprising a nucleotide sequence encoding SEQ ID NO:49.
 9. The isolatedpolynucleotide of claim 8, wherein said nucleotide sequence comprisesSEQ ID NO:48.